Micro-Infrared Spectroscopy of Insoluble Organic Matter Extracted from Primitive Chondrites
Résumé
Most of the organic matter in primitive chondrites consists in Insoluble Organic Matter (IOM). Its polyaromatic structure and isotopic compositions are consistent with a presolar origin [1]. Similar polyaromatic compounds have been reported in IDPs [2], STARDUST grains and Micrometeorites. The search of such compounds in both Interstellar Medium and comets requires to determine the optical properties of IOMs and to find a link between their spectroscopic variations and their geological history. To date, it has been established that large isotopic, compositional and structural [3] variations of IOMs depend on post-accretion processes, and possibly heterogeneity in the accreted precursors. We measured mid-infrared spectra (4000-650 cm-1) at E.S.R.F. on ID21 beamline. IOMs were extracted with a HCl/HF attack by continuous filtration. The IOM was then flattened on a BaF2 window. Absorption spectra were acquired in transmission through a confocal microscope. IOMs from unmetamorphosed carbonaceous chondrites have typical spectra of kerogen-like compounds [4]. We will present a classification of IOMs extracted from 3 CI, 6 CM mostly based on aromatic, oxygenated and hydrogenated functions bands.